What is it about?

Compound drought and heat wave (CDHW) events refer to situations wherein a region experiences both prolonged hot temperatures and drought (e.g., shortage of water) events. Compound drought and heatwaves (CDHWs) severely threaten socioecological systems, leading to greater impacts, e.g., wildfires, crop failure, and heat-related mortalities, than individual extremes. This topic is timely as we witnessed severe CDHW events in California and the southwest United States, Europe, and China in 2022, while the “black summer” of 2019/2020 in Australia remains a profound example of this threat.

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Why is it important?

The researchers compared two contrasting socioeconomic pathways: the high-end or worst-case scenario, wherein society fails to mitigate the effects of anthropogenic climate change, and a moderate scenario, wherein some conservative measures are put in place and efforts are made to abide by them. In the worst-case scenario, they found that by the late 21st century approximately 20% of global land areas are expected to witness approximately two CDHW events per year. These events could last for around 25 days and a fourfold increase in severity. Comparatively, the average CDHW frequency over the recently observed reference period was approximately 1.2 events per year, lasting less than 10 days, with far less severity.


The researchers emphasize the profound threat posed by more frequent and intense CDHW events in the coming decades and the dependence the emissions pathway chosen has on the severity of these events. As climate change continues to unfold, addressing the escalating risks associated with CDHW events becomes crucial. This study contributes to the growing understanding of the projected changes in CDHWs and highlights the need for proactive measures, including emission reductions and adaptation strategies, to build resilience and safeguard vulnerable regions from the impacts of compound drought and heat wave events.

Ashok Mishra
Clemson University

Read the Original

This page is a summary of: Climate change will accelerate the high-end risk of compound drought and heatwave events, Proceedings of the National Academy of Sciences, July 2023, Proceedings of the National Academy of Sciences,
DOI: 10.1073/pnas.2219825120.
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